Ladle slag or LMF slag has been recovered from the steel industry and reused as a slag conditioner for some period of time. Typically, in steel mills, the process for recovering ladle slag is as follows: the ladle slag is created in an LMF or ladle metallurgy furnace by scraping off old furnace slag, and adding fresh slag components to build a cleaner synthetic slag. In some shops, the old slag is treated with aluminum or other deoxidizers to create the same effect. The ladle slag functions to act as a refining aid for the steel in the ladle. Once this refining process is complete, the ladle is moved to a continuous caster. The ladle, at this stage, is opened from the bottom and the steel is drained from the ladle into a tundish and into a continuous caster. As the steel exits from the bottom of the ladle into the tundish, the ladle slag floats on top of the steel in the ladle. The ladle will reach a point when it is nearly empty and some slag may start showing up in the steel. At this point, or some time before this point, the slag gate is closed to shut off the flow of steel into the tundish. The ladle is then removed and the spent ladle slag, along with any remaining steel, is dumped into a slag pot, where it cools. This process is repeated again and again, with steel and slag being layered on top of one another into slag pots. Typically, a slag pot will hold from 3 to 5 taps of spent ladle slag and steel.
Normally, these slag pots are allowed to cool and are tipped over and quenched with water. The reason this product is generally quenched with water is that many spent ladle slags are unstable and exhibit "falling slag" characteristics. The characteristic of a falling slag is that the slag undergoes a phase change at some stage in the cooling process and turns from a solid into a powder. The effect of this is that some portion of the ladle slag falls to a very fine dry powdery dust which becomes an environmental nuisance, and creates difficulty in the rehandling and reuse of ladle slag handled in this conventional manner. For this reason, the slag pots are almost always quenched with water such that any falling slag produced will be wet and will not create an environmental (dusting) problem. Once the slag pot content is quenched and cooled, it is then crushed, the metal is removed for reuse and what is left is typically the spent ladle slag. Prior art in the reuse and reclamation of this ladle slag requires that the slag be crushed and dried and screened for reuse. Because the slag has been soaked with water, it hydrates, creating water of hydration in the slag. Ladle slag that is recovered by this technique is difficult to reuse for three reasons:
1. the slag is hydrated through its contact with moisture and contains undesirable amounts of crystalline moisture and free moisture; PA1 2. the slag contains more fine particles than is desired due to the falling nature of the slag which creates powder; PA1 3. the quenching produces a very wet product which requires energy and cost to dry the free moisture from the product.
An object of the invention is to provide a method of recovering ladle slag in which the above-referenced problems are at least partially addressed.